Known spray dry systems use high-pressure pumps that spray liquid products through dryer atomizing nozzles into dryers that produce powders. Quality of the powder can be compromised by bacteria in the liquid product that is converted to powder during spray drying. In order to try reducing bacteria count for increasing dryer yield and quality of the powder, efforts have been made to preheat the liquid product with heat exchangers upstream of the high-pressure pumps and therefore at low pressures.
In known implementations, arranging heat exchangers in low-pressure zones or upstream of the high-pressure pumps is done because typical heat exchangers are configured to operate at relatively low pressures since these typical heat exchangers can have somewhat delicate structures that make them suitable for rapid and efficient heat transference across their materials. Some implementations use multiple parallel heat exchangers in the low-pressure zone to provide greater surface area for a transfer, which further slows down flow rate to relatively low velocities. Preheating with heat exchangers upstream of the high-pressure pumps allows the liquid product to be exposed to high temperatures for relatively long periods of time because the liquid product flows at relatively slow velocities in the low-pressure zone upstream of the high-pressure pumps, especially with parallel heat exchanger implementations.
However, preheating liquid product for relatively long periods of time can have certain drawbacks, including potential powder quality compromises and requiring frequent cleaning of system equipment. Exposing liquid product to elevated temperatures for too long can reduce the quality of the final powdered product. The slow velocity flow rates of the liquid product through the heat exchangers can lead to fouling of the heat exchangers, which requires cleaning before further use. Furthermore, arranging heat exchangers upstream of the high-pressure pumps typically spaces this location is heating relatively far distances away from the dryers themselves. Typically, the dryer atomizing nozzles are located on the tops to the dryers. The dryer atomizing nozzles highly are highly elevated compared to lower floors at which the high-pressure pumps are installed, with the beat exchangers upstream of the high-pressure pumps spaced even further from the dryer atomizing nozzles. The far distances between and long travel time required for the heated liquid product to reach the dryers can lead to substantial decreases in temperature of the previously heated liquid product before atomization, which can reduce the effectiveness of the preheating.